1. Field of the Invention
This invention relates to devices for dispensing and mixing liquids, and more particularly to such devices that dispense and mix chemicals, and even more particularly to devices that dispense and mix cleaning chemicals.
2. Prior Art
It is common practice to purchase concentrated cleaning chemicals and to mix them with other liquids such as water to achieve the desired usage concentration for cleaning. A variety of proportioning dispensers have been developed to achieve this. The dispensers often employ venturi-type devices sometimes called eductors to draw the concentrated liquid chemical and mix it with the water stream. Examples of such eductors include the Sand U.S. Pat. Nos. 5,522,419, 5,253,677 5,159,958, and 5,862,829 all of which are assigned to the Assignee of the present invention and are expressly incorporated herein. Water traveling through the central, constricted portion of the venturi creates suction which draws the concentrated liquid chemical into the water stream.
The structure of such eductors is generally fixed, and thus, for a given water stream flow rate, the amount of concentrated liquid chemical drawn is a function of the fluid resistance in the flow path of the concentrated liquid chemical. Adjusting the amount of chemical educted is generally controlled by a metering orifice interposed into the flow path of the concentrated liquid chemical. Such orifices may be fixed or adjustable to vary the proportionate flow. Achieving the proper proportion of chemical merely with selection of a metering orifice is complicated by factors which vary per the application, such as the desired usage concentration, the viscosity of the concentrated liquid chemical, and the pressures at which the liquids are provided. Using metering orifices to control dilution means that very small metering orifice sizes are required, as shown in Table 1.
Metering orifices generally achieve dilution ratios of 2:1 to 300:1. More dilute mixtures are constrained by the volume rate of water available and by the smallest practical size of the metering orifices. Very small orifices are susceptible to clogging such as from contaminant particles or artifacts in the concentrated chemicals. In addition, the viscosity of the chemical imposes a size limitation. Introducing a fixed pressure drop to the overall dimensioning of the chemical feed line, or supply conduit, to achieve more dilute concentrations would preclude applications requiring less dilute concentrations.
Active devices which could monitor the relative amount of liquids being mixed and control dispensing are impractical as being uneconomical, increasing the cost of producing the dispenser. Moreover, providing such active devices with a power supply such as batteries or an electrical outlet is generally uneconomical or inconvenient. Moreover, dispensing devices often dispense conductive or corrosive materials that would further complicate protection of electronic components of an active system. Consequently, passive dispensing devices are generally used, even though this constrains the range of achievable usage concentrations.
Consequently, appropriate chemicals for dispensing are not concentrated as much as would be desirable, imposing additional costs of shipment. Dispensing devices for such less-concentrated liquid chemicals are thus required to have provisions for larger storage of chemicals and/or more frequent refills. In addition, at the more dilute end of the generally achievable range of operation, the metering orifice is susceptible to clogging, allowing defective mixtures to be generated. Moreover, certain types of chemicals that tend to have suspended solids are precluded from being dispensed at all by such devices.
Accordingly, it is an object of the present invention to provide an ultra-lean dilution apparatus for proportioning minute quantities of a first fluid, such as a concentrated cleaning solution, for mixing into a second fluid, such as tap water, which provides improved performance and which can be manufactured by assembling several molded components with little or no machining.
According to the principles of the present invention and in accordance with the described embodiments, the present invention provides a dilution apparatus for providing a selective pressure drop in a conduit by including a plurality of dilution disks, each dilution disk acting as a channel carrier by including a tortuous path of sufficient cross-sectional area to be resistant to clogging and having a sufficient number of sharp turns to create a desired pressure drop.
For ultra-lean dilutions of 350:1 to 1500:1, using metering orifices would require openings smaller than 0.010 inches in diameter. Yet in this range many particles or artifacts in chemicals may clog them. Thus, such metering orifices are generally not used. On the other hand, the disk channel formed herein from a plurality of tortuous paths would be several time larger than 0.010, as shown in three illustrative examples in Table 2. Thus, the channel is of a size to pass such particles or artifacts which would otherwise clog orifices in at least part of the noted range yet still produce the pressure drop necessary to produce the ultra-lean proportion.
While each disk produces a predetermined drop, the serial configuration of the tortuous paths of the plurality of dilution disks is additive to produce a range of dilution suitable for the chemicals used. In other words, disks are selectively inserted or withdrawn from the circuit to vary the pressure drop between the concentrated chemical and the carrier fluid and so vary the proportion of the mix.
In one embodiment of the invention, the tortuous path of a first of the plurality of dilution disks is recessed into a front face so that bringing the front face of the first dilution disk in contact with a back face of a second dilution disk completes the tortuous path. Furthermore, a blind intake of the tortuous path of the second dilution disk selectively communicates with an output port of another tortuous path on a front face of the first dilution disk.
In a further aspect of the invention, the desired pressure drop across the dilution apparatus is selectable by adding additional dilution disks and/or by varying the length and multiplicity of turns included in the tortuous path.
For example, given a predetermined number of dilution disks with a given tortuous path characteristic, a user selectable dilution control is provided by including a bypass for one or more pairs of dilution disks. More particularly, an output port and a blind intake are provided on each dilution disk, such that in an engaged position the output port and the blind intake of one dilution disk aligns respectively to a downstream blind intake and an upstream output port, placing the tortuous path in series. Furthermore, the dilution disk has a bypass position such that the upstream output port communicates via the intervening output port of the interposed dilution disk with the downstream blind intake without going through the tortuous path.
In yet a further aspect of the invention, a stack of dilution disks molded from economical elastomeric material are compressed together within an engagable housing including a window access for selectively positioning or rotating each disk into or out of the fluid circuit and to verify the setting of each disk, wherein, once engaged, the housing locks the disks into position. Advantageously provided are a positioning tab and an alignment tab, both peripherally located on each disk. The positioning tab allows for rotatably positioning, and verifying the position, of each disk within the window of the housing. The alignment tab cooperates with an alignment groove within the housing to constrain the range of rotation of each disk such that the two rotation extremes allowed correspond to an engaged and a bypass position for the disk.
In an additional aspect of the invention, a dilution reference is provided to indicate the relative dilution ratio based on the position of the positioning tabs.
In yet another aspect of the invention, a rotatable dilution disk is separated from another rotatable dilution disk by a fixed dilution disk, wherein the respective alignment tab is substantially constrained by the alignment groove of the housing. Movement of a rotatable dilution disk is thus prevented from inadvertently moving other rotatable dilution disks.